Mast materials

Still a bit sour about my spoiled trip I took a good look on the broken mast. And what I saw puzzeled me. A clean sharp fraction (exactly at the point where the screwthread begins) with a mysterous line in the middle. I also spotted some brass coulored particles in the material. What also puzzels me is that if there is no damage done to the mast (what I believe) how can it break at that point?
So my questions are:
What kind of steel are the masts made of?
And is there no better alternative that combines strength and stiffness with flexibility? (Maybe a composite material?)